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Question

如何在Swift 3/4中替换或重复数组的特定项目（v）：

["A","s","B","v","C","s","D","v","E","s"]

得到这个：

["A","s","B","v","v","C","s","D","v","v","E","s"]

或者这个：

["A","s","B","v","v","v","C","s","D","v","v","v","E","s"]
["A","s","B","v","v","v","v","C","s","D","v","v","v","v","E","s"]

原因是元素v在音频文件（A，B，C，...）之间插入了暂停（秒）。项目v的重复次数应通过SegmentedControl（1,2，...，6）设置。

Answer 1

快速外卖

extension Array where Element == String  {
    func repeatItem(_ item: Element, times n: Int) -> Array<Element> {
        return flatMap { $0 == item ? Array(repeating: $0, count: n) : [$0]     }
    }
}

详细说明

使用flatMap：

yourArray.flatMap { $0 == "v" ? [$0, $0] : [$0] }

基本上，这会检查数组的每个元素。如果是"v"，请将其变成["v", "v"]。如果不是"v"，则将其转换为具有单个元素的数组。然后它将所有这些数组展平，因此flatMap。

您还可以将特定项目增加三倍：

yourArray.flatMap { $0 == "v" ? [$0, $0, $0] : [$0] }

或重复n次：

yourArray.flatMap { $0 == "v" ? Array(repeating: $0, count: n) : [$0] }

使用游乐场进行验证：

//: Playground - noun: a place where people can play
import Foundation

var inputArray = ["A","s","B","v","C","s","D","v","E","s"]
var expectArray2 = ["A","s","B","v","v","C","s","D","v","v","E","s"]
var expectArray3 = ["A","s","B","v","v","v","C","s","D","v","v","v","E","s"]
var expectArray4 = ["A","s","B","v","v","v","v","C","s","D","v","v","v","v","E","s"]

extension Array where Element == String  {
    func repeatItem(_ item: Element, times n: Int) -> Array<Element> {
        return flatMap { $0 == item ? Array(repeating: $0, count: n) : [$0] }
    }
}

print(inputArray.repeatItem("v", times: 2) == expectArray2)
print(inputArray.repeatItem("v", times: 3) == expectArray3)
print(inputArray.repeatItem("v", times: 4) == expectArray4)

Answer 2

您可以使用insert(:at:)并使用元素的特定索引。

var foo = [0,1,2,3,4,5,6,7]
foo.insert(0, at: foo[0])

输出

[0，0，1，2，3，4，5，6，7]

您可以将其包装在函数中，以根据需要重复多次。

Answer 3

let array : [String] = ["A","s","B","v","C","s","D","v","E","s"]
print(replaceItem(array: array, item: "v"))

//Method

func replaceItem(array : [String], item : String) -> [String] {
    var newAr: [String] = []
    for arItem in array{
        newAr.append(arItem)
        if arItem == item {
            newAr.append(arItem)
        }
    }
    return newAr
}

输出： [“ A”，“ s”，“ B”，“ v”，“ v”，“ C”，“ s”，“ D”，“ v”，“ v”，“ E”，“ s”] < / p>

重复数组的特定项目

3 个答案:

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详细说明